A Novel Splitting-Beam Laser Extensometer Technique for Kolsky Tension Bar Experiment

A modified laser occlusive extensometer technique was developed to measure the specimen strain with reasonably high and tunable resolutions in Kolsky tension bar experiments. This new technique used a novel concept where a laser beam was split into two independent sections to track the displacement histories of the incident and transmission bar ends, respectively, with independent resolutions. This technique ensures highly precise small strain measurements without sacrificing the capacity for large strain measurement. The uncertainty caused by rigid body motion of the specimen during dynamic strain measurement, which is induced by slight variation of laser intensity along the gage length, was also minimized in this technique. The validation test on Vascomax ® maraging C250 alloy demonstrated that the new technique was capable of making both small and large strain measurements in Kolsky tension bar experiments, which is also applicable to Kolsky compression bar experiments.